I'm looking to finish the exhaust on my OM603 powered S123. I don't have a good reference for the stock exhaust diameter.
Looking on this forum I've found references to a 2.5" and a 3" exhaust.
I have a lead on a stock downpipe from an 87 300TD and it looks like it will fit. But I still need to have the rest of the exhaust fabricated.
I'm looking at having one of these resonators put in.
https://www.borla.com/products/universal-resonators/